Generally, a typical semiconductor light emitting device has a light emitting region containing ultraviolet, blue and green regions. In particular, a GaN-based light emitting device may be used for an optical device of a blue/green light emitting diode (LED), and an electronic device with high speed switching and high output power performance such as a metal semiconductor field effect transistor (MESFET), a hetero junction field effect transistor (HEMT), etc.
FIG. 1 is a cross-sectional view of a related art light emitting device 10.
Referring to FIG. 1, the related art light emitting device 10 is configured such that an n-type GaN layer 13, an active layer 15, and a p-type GaN layer 17 are sequentially stacked on a substrate 11 that is mainly formed of sapphire or SiC.
Silicon is doped into the n-type GaN layer 13 for reducing a drive voltage, and magnesium (Mg) is doped into the p-type GaN layer 17. The active layer 15 has a multi quantum well (MQW) structure. After an etching process is performed so as to expose a portion of the n-type GaN layer 13, a first electrode 19 is formed on the n-type GaN layer 13, and a second electrode 21 is formed on the p-type GaN layer 17.
When current is supplied to the light emitting device 10 from the outside through the first and second electrodes 19 and 21, light is emitted from the active layer 15.
The sapphire substrate 11 has a different lattice constant and crystal lattice from that of the n-type GaN layer 13 formed thereon. Accordingly, lattice mismatch such as dislocation, vacancy, etc, may occur at a boundary between the sapphire substrate 11 and the n-type GaN layer 13.
Thus, research is being advanced to reduce the lattice constant difference between the substrate 11 used in a light emitting device 10 and the nitride layer formed on the substrate 11, and to achieve good crystal lattice match therebetween.